Method of inhibiting corrosion and deposition in aqueous systems

Abstract

A corrosion inhibition and scale control method and composition are disclosed. The method comprises, adding to a cooling water system, for which protection is desired, a water soluble zinc salt, a cellulose gum material and an organo-phosphorus acid compound. Optionally, a corrosion inhibitor compound such as a 1,2,3-triazole or thiazole compound may be added to afford additional protection. Molybdate salts may also be included as optional corrosion inhibitors.

I claim: 
     
       1. Method of treating cooling water systems having a pH of about 8 or greater so as to inhibit scale formation on, and corrosion of, metallic parts in contact with said water system, said method comprising the steps of adding to said cooling water system, based on one million parts of said cooling water system, (1) a water soluble zinc compound adapted to liberate from about 0.1 parts per million to about 15 parts per million of Zn +2  ions in solution;   (2) from about 0.5 to about 50 parts per million of a water soluble sodium carboxymethylcellulose having a viscosity of less than about 200 centipoise (2% gum solution concentration, measured at 25° C.); and   (3) from about 0.2 to about 50 parts per million of an organo-phosphorus acid compound or water soluble salt thereof; said organo-phosphorus acid compound comprising a member or water soluble salt of such member selected from the group of compounds represented by the formulas ##STR12## wherein R is lower alkyl having from about one to six carbon atoms, substituted lower alkyl of 1-6 carbon atoms, a mononuclear aryl radical, or substituted mononuclear aromatic; M is a water soluble cation; R 1  is alkylene having from 1 to about 12 carbon atoms or a substituted alkylene having from about 1 to about 12 carbon atoms; R 2  is a lower alkylene having from about one to four carbon atoms, or an amine or hydroxy substituted lower alkylene; R 3  is H, OH, NH 2 , substituted amino, an alkyl having from one to six carbon atoms, a substituted alkyl of from one to six carbon atoms (e.g., OH, NH 2  substituted), a mononuclear aromatic radical and a substituted mononuclear aromatic radical (e.g., OH, NH 2  substituted); R 4  is R 3  or the group represented by the formula ##STR13## where R 5  and R 6  are each hydrogen, lower alkyl of from about one to six carbon atoms, a substituted lower alkyl (e.g., OH, NH 2  substituted), hydrogen, hydroxyl, amino group, substituted amino group, a mononuclear aromatic radical, and a substituted mononuclear aromatic radical (e.g., OH and amine substituted); R 7  is R 5 , R 6 , or the group R 2  --PO 3  M 2  (R 2  is as defined above); n is a number of from 1 through about 15; y is a number of from about 1 through about 14; R 10  is H, CH 3 , or C 2  H 5  ; R 8  is H, a straight or branched alkyl residue having from 1-18 carbon atoms, a cycloalkyl residue having from 5-12 carbon atoms, an aryl residue, an alkylaryl residue, or a residue of the formula: ##STR14## wherein R 10  has its previous significance and the sum of n+m is an integer of at most 100, or a residue --OX wherein X is hydrogen or a straight or branched alkyl residue having 1-4 carbon atoms and; R 9  is a residue --OX, wherein X has its previous significance.   
     
     
       2. Method as defined in claim 1 wherein said organo-phosphorus acid comprises 1-hydroxyethylidene 1,1-diphosphonic acid. 
     
     
       3. Method as defined in claim 1 wherein said organo-phosphorus acid compound comprises 2-phosphonobutane 1,2,4-tricarboxylic acid. 
     
     
       4. Method as defined in claim 1 wherein said organo-phosphorus acid compound comprises nitrilo-tris(methylene phosphonic acid). 
     
     
       5. Method as defined in claim 1 wherein said organo-phosphorus acid compound comprises a phosphinocarboxylic acid compound having the formula ##STR15## wherein Z is H or a cation, and wherein the sum of n+m=2 to 6. 
     
     
       6. Method as defined in claim 1 wherein said organo-phosphorus acid compound comprises hexamethylene diamine-N,N,N',N'-tetra (methylene phosphonic acid). 
     
     
       7. Method as defined in claim 1 wherein said organo-phosphorus acid compound comprises a mixture of 1-hydroxyethylidene 1,1-diphosphonic acid and 2-phosphonobutane 1,2,4-tricarboxylic acid. 
     
     
       8. Method as defined in claim 1 further comprising, adding to said water system, an effective amount of a corrosion inhibitor compound selected from the group consisting of effective azole compounds and effective molybdate compounds. 
     
     
       9. Method as defined in claim 8 wherein said corrosion inhibitor compound comprises tolyltriazole. 
     
     
       10. Method as defined in claim 8 wherein said corrosion inhibitor compound comprises mercaptobenzothiazole. 
     
     
       11. Method as defined in claim 1 wherein said organo-phosphorus acid compound (3) is added in an amount of between about 0.2 to about 15 ppm, said zinc compound (1) being added in an amount of between about 0.1 to about 10 ppm, and said sodium carboxymethylcellulose (2) being added in an amount of between about 1 ppm to about 25 ppm.